DEFENSIVE FERMENTS OF THE ANIMAL ORGANISM 3 



cated substance of its specific properties. The dis- 

 harmonious product is decomposed into indifferent 

 by-products which are harmless to the cell. More 

 energetic means are often employed, and the material 

 is oxidized or reduced according to the special needs 

 of the cell. Even in these simple forms of life it is 

 probable that many substances are rendered harm- 

 less by combining to form fresh compounds, just as, 

 in the metabolism of a more complicated organism, 

 rearrangements of different kinds are undergone 

 which alter such materials as are undesirable, so 

 that they may be excreted in this form out of the 

 body. Very often a given substance is incapable 

 of combination, in which case it must first be 

 so transformed by special processes as to be sus- 

 ceptible to combination. We thus see how the 

 cells of the body oxidize, reduce, or decompose, 

 until a product is reached that is capable of com- 

 bination. There is no reason to doubt that uni- 

 cellular organisms have similar means of defence at 

 their disposal, but they are not so easily traced, owing 

 to the fact that it is more difficult to add certain 

 substances to a single cell, without damaging it, than 

 it is in the case of a more complicated organism. 

 The latter are able to modify profoundly the action 

 of substances introduced by the mouth, owing to the 

 fact that they are gradually absorbed. Further, these 

 substances are considerably diluted in the lymph 



